Ever tried sorting numbers ? Yes ?
Have you ever tried sorting numbers, with thousand separators, and in numerical
order ?
A little harder, I think ! I found the same whilst writing some code for a
program,until I discovered a way to do it. The slow way is to convert the existing
string in the TListView to remove the separator, sort it, and then re-insert the
separator.
However, there is another way. It is based on the method above, but with one
crucial difference. The trick is to convert the numbers, but then to assign it to a
temporary double-length integer, run the sort, and output the result. The
separators in the numbers shown on screen are never removed - their order is
changed based on the temporary conversion. Below is some example code - it uses
example filenames and filesizes to demonstrate the sorting procedure.
To see this in action, you need to:
1. Start a new project, and add a TListView to a TForm.
2. Add a few example filenames in column 0, then some example filesizes in column 1.
3. Add / change the code, to match the code below.
4. Run the project.
Notes:
- The code can be adapted to use different columns, depending on your requirements
- as long as the right column numbers are assigned, then it should still work OK.
- To change the direction of the sorting on the first click, change the
ListView1.Tag numbers in the Object Inspector.
- ListView1.Tag numbers: -1 = reverse order; 1 = forward order.
- It should be noted that the ',' symbol is being used as the thousand separator -
this can also be changed from the sThouSep constant declaration
CODE FOR SORTING NUMBERS WITH SEPARATORS:
1 unit cdSortNumbers;
2
3 interface
4
5 uses
6 SysUtils, Classes, Forms, Controls, ComCtrls;
7
8 type
9 TForm1 = class(TForm)
10 ListView1: TListView;
11 procedure bySizeClick(Sender: TObject);
12 procedure ListView1ColumnClick(Sender: TObject; Column: TListColumn);
13 private
14 { Private declarations }
15 public
16 { Public declarations }
17 end;
18
19 var
20 Form1 : TForm1; { main form }
21 n1 : double; { used to assign converted numbers to double length integers,
22 before conversion }
23 n2 : double; { n1 = first number in pair, n2 = second number in pair }
24
25 const
26 sThouSep = ','; { defines the thousand separator being used in TListView -
27 change if required }
28
29 implementation
30
31 {$R *.dfm}
32
33
34 { main sorting function - convert strings to numbers, then sort accordingly }
35 function CustomSizeSortProc(Item1, Item2: TListItem; ParamSort: integer): integer;
36 stdcall;
37 begin
38 n1 := 0;
39 n2 := 0;
40
41 { string conversion and assignment process to n1 or n2, based on order being
42 sorted }
43 if ParamSort = 1 then
44 begin
45 n1 := StrToFloat(StringReplace(Item1.SubItems.Strings[0], sThouSep, '',
46 [rfReplaceAll]));
47 n2 := StrToFloat(StringReplace(Item2.SubItems.Strings[0], sThouSep, '',
48 [rfReplaceAll]));
49 end
50 else if ParamSort = -1 then
51 begin
52 n1 := StrToFloat(StringReplace(Item2.SubItems.Strings[0], sThouSep, '',
53 [rfReplaceAll]));
54 n2 := StrToFloat(StringReplace(Item1.SubItems.Strings[0], sThouSep, '',
55 [rfReplaceAll]));
56 end;
57
58 { determines final position, based on comparing results from conversion process }
59 if n1 > n2 then Result := 1 else if n1 < n2 then Result := -1 else Result := 0;
60 end;
61
62 { determine direction of sort, then call sort function }
63 { can be called from other components, such as a TButton }
64 procedure TForm1.bySizeClick(Sender: TObject);
65 begin
66 if ListView1.Tag = -1 then ListView1.Tag := 1 else ListView1.Tag := -1;
67 ListView1.CustomSort(@CustomSizeSortProc, ListView1.Tag);
68 end;
69
70 { optional extra - calls sorting routine from column header click }
71 { if TListView being used to sort many numbers / strings, then these can be added
72 in a similar manner }
73 procedure TForm1.ListView1ColumnClick(Sender: TObject; Column: TListColumn);
74 begin
75 if column = ListView1.Column[1] then bySizeClick(Sender);
76 end;
77
78 end.
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